Photoflash lamp

ABSTRACT

A percussive-type photoflash lamp in which the inner wall of the lamp envelope is provided with an indicator spot containing a fluorescent dye sensitive to the combustion products of the fulminating material of the primer in order to permit automated inspection and rejection of those lamps or subassemblies thereof during manufacture in which the fulminating material has been flashed inadvertently.

United States Patent inventor John W. Shaffer Williamsport, Pa.

Appl. No. 878,164

Filed Nov. 19, 1969 Patented Dec. 7, 1971 Assignee Sylvanla Electric Products Inc.

PHOTOFLASH LAMP 3 Claims, 1 Drawing Fig.

US. Cl 431/13, 431/93 Int. Cl F211: 5/02 Field 01 Search 431/93, 94,

[56] References Cited UNITED STATES PATENTS 2,046,388 7/1936 Kurlander 431/94 2,599,644 6/1952 Keukens... 431/94 2,781,654 2/1957 Pipkin 431/94 Primary Exdminer- Edward J. Michael Attorneys-Norman J. O'Malley and Joseph C. Ryan ABSTRACT: A percussive-type photoflash lamp in which the inner wall of the lamp envelope is provided with an indicator spot containing a fluorescent dye sensitive to the combustion products of the fulminating material of the primer in order to permit automated inspection and rejection of those lamps or subassemblies thereof during manufacture in which the fulminating material has been flashed inadvertently.

PATENTED [1E8 7|97| 3 525540 JOHN W SHAFFER INVENTOR BY! Q ATTOR Y PHOTOFLASl-l LAMP This invention relates to the manufacture of photoflash lamps and more particularly to those of the percussive type.

Generally speaking, a percussive-type photoflash lamp comprises an hermetically sealed, light-transmitting envelope containing a source of actinic light and having a primer secured thereto. More particularly, the percussive-type photoflash lamp may comprise a length of glass tubing constricted to a tip at one end thereof and having a primer sealed therein at the other end thereof. The length of glass tubing which defines the lamp envelope contains a combustible such as shredded zirconium foil and a combustion-supporting gas such as oxygen. The primer may comprise a metal tube and a charge of fulminating material on a wire supported in said tube.

The fulminating material generally comprises a mixture of red phosphorous, potassium chlorate and a powdered metal such as zirconium. lt must be extremely sensitive to impact ignition to insure high lamp reliability of flashing with the desirably low impact energies delivered by the firing mechanism. At the same time, the metal tube of the primer is thin-walled and softso as to minimize the required impact and afford the maximum lamp reliability. Operation of the percussive-type photoflash lamp is initiated by an impact onto the tube to cause deflagration of the fulminating material up through the tube to ignite the combustible disposed in the lamp envelope.

Although the fulminating material must have a very high impact sensitivity in order to insure the reliability of lamp flashing in the finished product, it presents very substantial problems and difficulties with respect to the manufacture and handling of individual lamps in a high speed, mass production operation. Very minor bumping or jarring of the intermediate product structure of the lamp during its manufacture can cause the fulminating material to flash. If such accidental flashing of the fulminating material occurs prior to the introduction of the compressed oxygen atmosphere into the intermediate product structure, it goes unnoticed because the shredded combustible, even if present, does not burn. Such lamps with spent fulminating material are, of course, inoperative.

The foregoing problem is unique to flashlamps of the percussivetype. Conventional filament-ignited flashlamps may be subjected to electrical continuity checking of the filament lead wire assembly and the beads of ignition paste are visible rather than concealed within a metal tube. On the other hand, nondestructive tests, such as visual or X-ray inspection of percussive-type photoflash lamps, fail to show whether or not the fulminating material has been discharged or flashed during lamp manufacturing operation. When destructive testing techniques, such as flashing of sample lamps, show a high incidence of lamps with preflashed material, the entire production group must be scrapped because the defective lamps cannot be segregated. Such losses make the manufacture of percussive-type photoflash lamps a formidable operation, increasing the cost of the finished product to the consumer and could result in unintentional marketing of defective lamps. While the occurrence of such inadvertent ignitions might possibly be avoided or minimized by handling the lamps with extreme care on an individual basis, the cost of such a procedure would be prohibitive.

in view of the foregoing, one of the principal objects of this invention is to greatly facilitate the manufacture of percussivetype photoflash lamps on high-speed automated equipment and at the same time provide the necessary quality control attendant such manufacture. More specifically, one of the principal objects of this invention is to facilitate the segregation of prematurely flashed primer assemblies at various stages during lamp manufacturing operations as well as thereafter.

One technique for segregating such lamps that proved to be of insufficient sensitivity and reliability involved an additive to the fulminating material that would impart a cloudy appearance to the lamp if inadvertent ignition occurred while the lamp contained air but which would not produce such an effect in a completed lamp filled with oxygen. Since the shreds are ignited when the fulminating material of a completed lamp is flashed, it is only necessary to be able to identify those lamps in which the fulminating material ignited when the lamp was air filled. Also, clouding in a completed lamp would reduce the light output and would be highly undesirable. Such agents as carbon black performed in this manner and burned to colorless carbon dioxide in the oxygen atmosphere of a completed lamp. It has been found however that such self-indicating fulminating mixtures do not reliably produce a readily observed discoloration. Limitations on the amount of indicator tolerable in the fulminating material because of resulting desensitization, and lamp-to-lamp variations in the weight of fulminating material, gave in all cases a percentage of lamps that in effect did not self-indicate. Also, burning of the finely divided carbon black in a lamp produced high internal gas pressures and uncertain lamp containment.

Another suggestion has been the formulation of certain organic dyestuffs which react with the minute quantities of phosphorous pentoxide given off by the burning fulminating material to produce a color change. A spot of such a dye-containing formulation may be applied to the inner wall of the lamp envelope. This spot has a given initial color. ln the event of an inadvertent firing of the fulminating material the color of the spot changes irreversibly to permanently indicate that this particular lamp is defective. Although this technique has the advantage that it affords the user an opportunity to inspect the lamp prior to using it, it is not adaptable to automated machine inspection of the lamps at various stages of their manufacture.

It has been found that certain fluorescent dyes cease to fluoresce in the presence of combustion products of percussive flashlamp fulminating material. Thus, a spotting fluid may be compounded from such a fluorescent dye, a suitable binding resin, a pH buffering agent and a humectant. Such spots are applied on the inner surface of the lamp envelope. Exposure to ultraviolet light causes the spots to fluoresce brightly, which fluorescence may be monitored with a photocell. Flashing of the fulminating material in the percussive flashlamp assembly causes a rapid and complete loss of fluorescence in the spot.

In a specific embodiment of the invention illustrated in the accompanying drawing, the single FlGURE is a sectional elevational view of a percussive-type photoflash lamp embodying the principles of this invention.

The lamp comprises a length of glass tubing defining an hermetically sealed lamp envelope 2 constricted at one end to define an exhaust tip 4 and shaped to define a seal 6 about a primer 8 at the other end thereof. The primer 8 comprises a metal tube 10, a wire anvil l2 and a charge of fulminating material 14. A combustible such as filamentary zirconium l6 and a combustion-supporting gas such as oxygen are disposed within the lamp envelope. The wire anvil 12 is centered within the tube 10 and held in place by a crimp 18 just above the head 20 of the anvil. Additional means, such as lobes 22 on wire anvil 12, are also used to aid in stabilizing and supporting it substantially coaxial within the primer tube 10 and insuring clearance between the fulminating material 14 and the inside wall of the tube 10. A refractory bead 24, fused to the wire anvil 12 just above the inner mouth of the primer tube It), eliminates bumthroughs and functions as a deflector to deflect and control the ejection of hot particles of fulminating material from the primer tube.

An indicator spotting fluid in accordance with the principles of this invention may have the following dried composition: dichiorofluorescein, 9.61 percent; sodium bicarbonate, 3.85 percent; glycerol, 38.46 percent; hydroxyethyl cellulose, 38.46 percent; and orthophenyl phenol, 9.61 percent. Suitable water is stirred into the mixture to give a suitable consistency for automated application. A small drop of this fluid is applied on the inner wall of the flashlamp envelope 2 to provide an indicator spot 26 and dried just prior to insertion of the wire anvil l2 coated with fulminating material 14 into the primer tube 10 in seal 6. Subsequently the combustible 16 is introduced into the lamp envelope 2, a constriction is drawn at the open end and the intermediate product is processed in the usual manner.

One of the principal advantages of this invention over the visual indicating spot suggested heretofore for flashed primer detection is that it permits automated inspection of the lamps during their manufacture and automated rejection of defective assemblies.

Although the specific embodiment described above has been found to be particularly advantageous, many variations thereof readily suggest themselves to one skilled in the art within the spirit and scope of this invention. For example, one may prefer to employ a spotting fluid which would not normally fluoresce but which, upon flashing of the lamp primer, would indicate the same by fluorescing. Other binding resins than hydroxyethyl cellulose may be used. For example, hydrolyzed polyvinyl alcohol affords excellent adhesion to glass. The requirements of such binding resins are water solubility and adherence to glass. Glycerol may be replaced with other humectant plasticizers such as di-, trior tetraethylene glycol. The weight ratio of humectant to resin is not critical and may be varied from 2 to 0.1. Similarly, the ratio of dye to resin may be varied from 0.1 to 1.0. The weight ratio of dye to sodium bicarbonate may be varied from to i.

What I claim is:

l. A photoflash lamp comprising:

an hermetically sealed, light-transmitting envelope;

a quantity of filamentary combustible material located within said envelope;

a combustion-supporting gas in said envelope;

a primer secured to and extending from one end of said envelope, said primer including a charge of percussion-sensitive fulminating material;

and means located within said envelope for indicating the functional condition of said fulminating material, said means comprising a fluorescent dye sensitive to the combustion products of said fulminating material both in the presence of and in the absence of said combustion-supporting gas.

2. The combination of claim 1 in which said indicating means is a spot formed from a fluid compounded from said fluorescent dye, a binding resin, a pH buffering agent and a humectant.

3. The combination of claim 1 in which said indicating means is a spot on the inner wall of said envelope, said spot being formed from a fluid having the following dried composition: dichlorofluorescein, 9.61 percent; sodium bicarbonate, 3.85 percent; glycerol, 38.46 percent; hydroxyethyl cellulose, 38.46 percent; and orthophenyl phenol, 9.61 percent. 

1. A photoflash lamp comprising: an hermetically sealed, light-transmitting envelope; a quantity of filamentary combustible material located within said envelope; a combustion-supporting gas in said envelope; a primer secured to and extending from one end of said envelope, said primer including a charge of percussion-sensitive fulminating material; and means located within said envelope for indicating the functional condition of said fulminating material, said means comprising a fluorescent dye sensitive to the combustion products of said fulminating material both in the presence of and in the absence of said combustion-supporting gas.
 2. The combination of claim 1 in which said indicating means is a spot formed from a fluid compounded from said fluorescent dye, a binding resin, a pH buffering agent and a humectant.
 3. The combination of claim 1 in which said indicating means is a spot on the inner wall of said envelope, said spot being formed from a fluid having the following dried composition: dichlorofluorescein, 9.61 percent; sodium bicarbonate, 3.85 percent; glycerol, 38.46 percent; hydroxyethyl cellulosE, 38.46 percent; and orthophenyl phenol, 9.61 percent. 